In a known conventional treatment for ventricular tachycardia in which an ablation catheter is percutaneously inserted between the heart and the pericardium (pericardial cavity), an access route through which the ablation catheter is inserted into the pericardial cavity from outside the body is provided by using a puncture needle (for example, see PTL 1).
This puncture needle is inserted into tissue under X-ray observation, and a distal end of the puncture needle is projected into the pericardial cavity and is deformed due to the resilience of a spring that is released when the puncture needle has passed through the pericardium.
Because the pericardium itself cannot be seen in X-ray images and the outline of the heart is unclear, it is impossible to directly determine whether or not the pericardium has been pierced in X-ray images. However, by using the above-described puncture needle, deformation of the distal end of the puncture needle can be observed in X-ray images, and thus, it is possible to determine that the puncture needle has penetrated through the pericardium.